Multiple-step polyclonal versus one-step monoclonal enzyme immunoassay in the detection of Helicobacter pylori antigen in the stools of children

Abstract

Objective: Evaluation of a polyclonal and a monoclonal Helicobacter pylori stool antigen test (HpSAT) for the detection of Helicobacter pylori (HP) infection in children.

Methods: 43 children underwent a 13C-urea breath test (13C UBT) and a HpSAT for the detection of HP. A child was considered HP positive if the 13C UBT was positive. Two HpSATs were tested: the "Premier Platinum HpSA" test (PP HpSAT) (polyclonal enzyme immunoassay) and the "ImmunoCard STAT! HpSA" test (ICS HpSAT) (one-step immunochromatographic assay).

Results: The mean age of the children was 8.9 y (range 3.5-17.5 y). Of the 43 children, 18 (41.9%) were HP positive and 25 (58.1%) were HP negative. The PP HpSAT showed a sensitivity of 94.4% and a specificity of 100.0%. With the ICS HpSAT, equivocal results occurred in 5/42 (11.9%) of the tests due to a problem with the visual interpretation of the change in colour of the test-line. The ICS HpSAT had a sensitivity of 100.0% and a specificity of 76.0% when the test was considered positive in case of any change of colour of the test-line, which is the correct practice according to the manufacturer. The ICS HpSAT had a sensitivity of 100.0% and a specificity of 96.0% when the test was considered positive only in case of a "significant change of colour" of the test-line.

Conclusion: Compared to the 13C UBT, the PP HpSAT shows a comparably good sensitivity and specificity, the ICS HpSAT has a comparably good sensitivity but lower specificity due to a high percentage of equivocal results when the test is used according to the manufacturer's instructions, and the ICS HpSAT has a comparably good sensitivity and specificity when a weakly positive test is considered negative for the diagnosis of HP infection in children. The ICS HpSAT is easy to perform with results available within 10 min, and is therefore of particular interest in ambulatory medicine.